The treatment of progressive late juvenile and adolescent idiopathic scoliosis remains controversial, with most spine specialists agreeing that alternatives to the standard of care in treating moderate yet progressing spinal deformity must be clinically studied. The disease progression is related to growth, but is otherwise of unknown and likely has multiple etiologies. Children with curves greater than 25 are recommended for bracing as the standard of care. Bracing is an attempt to arrest progression and avoid spinal fusion. When the curvature progresses beyond 40 or 50, a multiple level spinal fusion is the standard of care, with the intention of obviating the highly prevalent problems of pain and cardiopulmonary compromise in adulthood. Additionally, large curves can result in significant cosmetic deformity and associated psychological distress. Pooled studies of bracing compared to observation or watchful waiting have yielded evidence that bracing a growing adolescent with adolescent idiopathic scoliosis is equivalent to observation. Spinal fusion has been shown to be effective but is very invasive, expensive and has a high complication rate. A multi-center NIH NIAMS study of bracing effectiveness (BrAIST) has completed enrollment and is currently ongoing. The applicant believes the results of this study are unlikely to indicate that bracing is effective in the patient subpopulatin that qualifies for the proposed study. The goal of this research plan is to conduct a clinical investigation of a pediatric medical implan device (the HemiBridge System) designed to stop progressive idiopathic scoliosis. The long term goal of this research is to determine the clinical safety and probable benefit of the HemiBridge System in arresting idiopathic scoliosis progression during adolescent growth. The clinical study protocol design is limited to patients at the highest risk of progressing to needing multi-level fusion surgery. The scope of the phase 2 clinical study is to determine safety and probable benefit of the HemiBridge System in this patient population.